Electric driving means for sewing machines



P. G. BRYNGE ETAL 3,425,376

ELECTRIC DRIVING MEANS FOR SEWING MACHINES Filed June 15, 1964 Feb.4,1969

Sheet a INVENTORS Feb. 4, 1969 P. G. BRYNGE ET AL 3,425,376

ELECTRIC DRIVING MEANS FOR SEWING MACHINES Filed June 15, 1964 Sheet 2of 2 IN V EN TORS United States Patent 7,260/63 Us. or. 112-220 Int. Cl.Db 69/10; H01h 47/32; H02p 5/16 This invention relates to an electricdriving means for sewing machines, comprising at least two movable,cooperating working means, particularly a loop-taker and a sewing needleholder reciprocable in the longitudinal direction of the needle, atleast one of said working means being driven by a pulse motor. In thisspecification the expression pulse motor denotes electro-magnet motors,particularly with reciprocable motion, solenoid motors, electro-dynamicmotors, step motors and the like, which are driven by pulses.

A suitable driving means of this kind would provide obvious advantages,such as elimination of comparatively expensive, mechanicaltransmissions, e.g. between the needle-bar and the loop-taker, and greatliberty in the 20 Claims design of industrial sewing machines. Severalsuggestions for such driving means have also been made, e.g. comprisinga solenoid motor for the needle-bar and a commutator rotating togetherwith the loop-taker for the control of the current supply to said motorbut such suggested driving means have, as far as we are aware, found noemployment, probably on account of the fact that they have been tooexpensive, not permitted sufiiciently high sewing speed and/or notpermitted sufiicient synchronization of the working means. i

The principal object of the invention is to provide an improved drivingmeans of the kind above referred to. This and other objects are attainedprincipally by the provision of at least one contact-free pulsegenerator having a transducer movable in synchronism with the otherworking means for generating pulses in a pluse transmitter, and anelectronic, preferably contact-free control assembly which is connectedto a current source and preferably comprises semi-conductors, fortransforming through suitable adaption and treatment said pulses tocurrent pulses for driving the first-mentioned working means in stepwith said other working means.

In a particularly advantageous embodiment said one working means is asubstantially vertically reciprocable needle-holder driven by anelectromagnet motor having a reciprocable motion, and the other workingmeans is a loop-taker driven by an electric ordinary motor, connected tothe current source, having a speed which is manually adjustable down tozero, said needle-holder being arranged to be in its upper limitposition when the loop-taker is standing still and consequently nopulses are transmitted from the transmitter to the control assembly.This arrangement assists in improving the synchronization of saidworking means.

When the sewing machine is provided with a workfeeder for step-wisefeeding of the work, the driving means according to the inventionpreferably comprises a control means governed by the movement of theneedleholder towards the loop-taker for inhibiting the next feedingstep, when the needle-holder driven by the electromagnet motor onaccount of abnormally great resistance from the work has not reached itsstitch forming position with respect to the loop-taker.

In order to minimize the mass-forces (due to inertia) theelectromagnet-motor of the driving means according to the invention issuitably electrodynamic, preferably permanent-electrodynamic, itscurrent coil being axially ice movable in an annular air gap in a magnetbody, and secured to a rod projecting therethrough and preferablyconstituting said working means driven by said motor.

The invention will be more particularly described with reference to theaccompanying drawings, in which FIG. 1 is a diagrammatical side view ofa lock-stitch sewing machine according to the invention; and

FIG. 2 is a diagrammatic side view of an extended or generalized versionof the sewing machine according to FIG. 1 comprising a plurality ofworking means.

The frame of the machine shown in FIG. 1 comprises a base plate 1supporting the work, and a cantilever bracket-arm 2 with a head 3 whichmay be removable. In the head there is rigidly secured a permanentmagnet 4, possibly a ferrite magnet, having an annular air gap 5 for aniron-free driving coil 6 and a central bore for a substantiallyvertical, non-rotatable needle-bar 8 constituting a holder for a sewingmachine needle 9. The coil 6 is, preferably by means of a light frame10, suitably of plastic, secured to the needle bar 8, which is ofnonmagnetic material, suitably of stainless steel or aluminum, andsupported in bushings 11 in the magnet 4 or the head 3. The verticalmovement of the needle-bar is limited by stops 12, 13 which are providedon the needlebar and preferably adjustable in the longitudinal directionthereof. The stops 12, 13 cooperate e.g. with the bushings 11 and are ofan elastic material, such as rubber, said coil 6 being locatedsubstantially within the magnet 4 in its lower end position andsubstantially outside the magnet in its upper end position.

For forming lock-stitches the needle 9 may, as known in the art,cooperate with a rotating loop-taker 14 mounted on a spindle 15journalled below the base plate 1 and rotated by an electric motor 16.Below the needlebar 8 the base plate 1 has an opening 7 for awork-feeder (not shown in FIG. 1) which is movable vertically andhorizontally in a substantially rectangular path for indexing the workone step perpendicularly to the plane of the drawing, when the needlehas left the work after a stitchformation.

The coil 6 is through two leads 17, 18 which permit vertical movement ofthe coil, connected to an electronic, contact-free control assembly 19,20 which is through terminals A, B, C also connected to a current source21, comprising a transformer 22 which may be connectable to analternating current lighting system by means of a plug, two rectifiercircuits 23, and two capacitors 24. The current source 21 gives theterminals A, B, C different, low direct voltages, e.g. B 12 volts higherpotential than C but 12 volts lower potential than A. To thelast-mentioned end, the current source 21 may also be comprised of twobatteries connected in series. The electric motor 16 is connected to theassembly 21 through a potentiometer 25 which may be set or adjusted byhand or by foot for adjustment of the speed of the loop-taker 14, downto zero. The control assembly has associated with it an inductive pulsetransmitter 27 in the shape of an induction coil provided with an ironcore, and the motor 16 drives a transducer 26 in the shape of a wheel,with a permanent magnet 28 at its circumference, one revolution for eachoperation cycle of the loop-taker 14. The magnet 28 is substantiallyopposite to the transmitter 27 when the needle is in its lowermostposition and excites pulses in the coil of the transmitter 27 whenrotating. As an inductive pulse generator it is possible to utilize,instead of the members 26, 27, e.g. a pole wheel driven by the motor 16,or a coil with a permanent magnet, respectively. The control assembly19, 20 includes a bi-stable multivibrator circuit 19, preferably aSchmitt trigger comprising a variable resistor 29 and transistors 30,31, 32, and a repoling or intermittentl pole-reversing circuitcomprising a transformer 34 and transistors 35, 36.

When the loop-taker 14 is stationary, the coil 6 receives a directcurrent and is thereby maintained in its upper end position. When theloop-taker has been started by means of the potentiometer 25, themultivibrator circuit 19 is triggered by pulses from the pulsetransmitter 27. When the voltage at the transistor attains apredetermined value set by the potentiometer 29, the transistor isswitched from its conductive state to its non-conductive state, or viceversa, when receiving a pulse. When switching from one state to theother transistor 30 sets the other transistor 31 into the oppositestate. Hereby there is generated at the transistor 31 a substantiallyrectangular pulse which makes transistor 32 conductive, after whichtransistors 35, 36 through transformer 34 alternately become conductiveand non-conductive respectively and thereby re-pole or successivelyreverse the direction of current in the driving coil 6 which accordinglyreceives, in synchronism with the movements of the loop-taker 14, atrain of substantially rectangular current pulses of alternatingpolarity and without any (appreciable) intervals, whereby the needle-bar8 is normally reciprocated in synchronism with the movements of theloop-taker 14. A thread tightener or thread take up device on the armhead 3 (not shown in FIG. 1) may be driven mechanically from theneedle-bar 8 or electrically from the current source 21, as shown inFIG. 2.

If the needle-bar 8 during a downward motion should meet an abnormallygreat resistance from the work, it may happen that it will becomearrested by the work and not reach stitch forming position with respectto the looptaker 14. To obviate faulty stitches at such occurrences themachine may be provided with control means, governed by the downwardmotion of the needle-bar, for inhibiting the next indexing step, whenthe needle-bar 8 has not reached stitch forming position with respect tothe loop-taker. Such a device becomes as simple as possible if the workfeeder is not driven mechanically from the spindle 15 but is driven atleast in part electrically, e.g. if it is advanced, against thebiasingforce of a spring, by an electromagnet and is raised by a cam. Theabove-mentioned faulty stitch preventing control means may comprise apermanent magnet 37 which is attached to the needle-bar and in the lowerend position thereof, or at least when the needle has penetrated thework, faces an impulse transmitter 38 and excites an impulse thereinwhich after a suitable delay and possible amplification by means knownper se is applied to the electromagnet and energizes it when the needlehas left the work.

Such an expanded embodiment of the invention in which not only thework-feeder but also a thread take-up device are driven at least in partelectrically by means of impulses generated only when the needle-bar 8has reached stitch forming position is illustrated in FIG. 2.

The work feeder 40 of FIG. 2 is supported by a supporting slide 40a theleft hand end of which forms the armature of an electromagnet 42 fed bycurrent pulses. The slide 40a and the electromagnet 42 form together apulse motor. The work feeder 40 and the supporting slide 40a are movedin a substantially rectangular, closed path during each stitch formingcycle, that is are raised by a. cam 41 secured to the spindle 15(compare FIG. 1), are pulled leftwards (the work feeding stroke) by theelectromagnet 42 when it is energized, are lowered during the nextangular increment of the cam 41 and are finally retracted rightwards bythe return spring 48. The electromagnet 42 is supported by the armatureportion of the supporting slide 40a and a leaf spring 42a secured to anut member 43 which is maintained non-rotatable by guide means 43a. Thestroke of the Work feeder is limited by a stationary stop 60 at theright hand (return) end and a stop 61 at the left hand end of theelectromagnet 42. The position of the electromagnet and thelast-mentioned stop 61 and accordingly the length of the stitches isadjusted by means of a rotatable threaded bolt secured to an adjustmentknob 44.

The thread take-up device 51 is rotated upwards (clockwise) fortightening the thread by a rotary electromagnet 50 fed by current pulsesand is returned downwards by a spring (not shown). The rotary movementsof the takeup device 51 are limited by stops (not shown).

The current pulses for driving the rotary magnet 50 and accordingly thethread take-up device 51 in synchronism with the needle-bar 8 originatein a pulse transmitter comprising an annular permanent magnet 52 and acoil 53, both cooperate with a transducer in the shape of a magnetic orsoft iron piece 47 attached to the needle-bar 8. When the iron piece 47penetrates the coil 46 during the upward stroke of the needle-bar 8 acurrent pulse of one polarity which is utilized for energizing themagnet 50 is induced in the coil 46. Since the magnet 50 has its returnmovements imparted to itself by a spring, the current pulses of theopposite polarity which are generated during the downward stroke of theneedle-bar 8 and the iron piece 47 have to be eliminated or filteredoff. This could be brought about by a rectifier in a manner known perse. The pulses induced in the coil 46 are fed by the leads 63, 71 to theinput of a pulse shaping control assembly 59 which is similar to thecorresponding electronic control assembly 19, 20 of FIG. 1 with thesingle exception that the transformer 34 and the transistors 35, 36thereof have been replaced by a transistor 65a and an adjustableresistor 66a as shown in FIG. 2. The output pulses of the controlassembly 59 are applied to the rotary magnet 50 for energizing itthrough leads 67, 68.

In the same way the pulses for actuating the pull magnet 42 of the workfeeder are generated in a coil 53 cooperating with an annular permanentmagnet 52 and the transducer 47. These pulses are applied by leads 63,64 to a pulse shaping control assembly 49 similar to the assembly 59 ofthe thread take-up device and comprising a transistor 65b and anadjustable resistor 66b corresponding to members 65a and 66arespectively, instead of the transistors 35, 36 of FIG. 1. The outputpulses of the control assembly 49 are applied to the pull magnet 42 forenergizing it through leads 69, 70- corresponding to the leads 67 and 68respectively.

It is obvious that no pulses, at least no pulses of sufficientamplitude, are generated in the coils 46, 53, if the needle-bar 8 shouldnot reach stitch forming position, and accordingly undue operation ofthe thread take-up device 51 and the work feeder 40' is inhibited andfaulty stitches are thus prevented.

If the loop-taker 14 makes two revolutions per stich, the transducer 26may be driven mechanically from the spindle 15 at half of its speed. Thetransducer may also be arranged on the spindle 15 if the controlassembly is correspondingly designed, e.g. arranged to suppress everysecond pulse. In this instance the wheel 26 may be omitted and themagnet be attached directly to the looptaken 14.

Of course, other embodiments are possible within the scope of theinvention. Instead of an inductive pulse.

transmitter 27 it is also possible to utilize a photo-cell, a phototransistor or another light-electric pulse transmitter together with alight source and a transducer or trigger, e.g. in the shape of arotating shutter with an aperture passing before the transmitter and thewidth of which is adjustable for altering the width of the rectangularpulse. In inductive pulse generators the pulse width may be adjusted bythe use of one permanent magnet provided with adjustable pole pieces, orof two magnets which are adjustable with respect to each other. Thosepulses which actuate the driving coil 6 in the one direction could bemade longer or given a greater width than the other ones, e.g. tomaintain the driving coil at its one extreme position (the upper endposition) longer than at its other end position. When the demands uponthe driving means are comparatively restricted, one of the terminals A,B, C may be omitted, the assembly 21 may be simplified in acorresponding degree or be replaced by a single battery, the transistors35, 36 being replaced by a switching device for reversal of theconnection between the remaining terminals and the leads 17, 18-, andthe transformer 34 being omitted, a relay for the switching device and arectifier being then connected in parallel at the location of theprimary of the transformer. In zigzag sewing machines having a laterallyoscillating needlebar the magnet body 4 may be rigidly secured to alaterally oscillating bracket in the head 3-.

The invention may also be applied to sewing machines having anoscillating loop-taker or shuttle, possibly for driving said loop-takeror the like which is then not mechanically coupled to the transducer. Inthe embodiment illustrated, the needle-bar is driven electro-dynamicallyin both directions, and the mass-forces (due to inertia) are minimized.The needle-bar may also, generally to less advantage, be driven by aspring in the one direction (upwards) and electro-dynamically in theother, the control assembly 19, 20 then being arranged to supplyrectified pulses to the coil 6 at intervals corresponding to theoperation of the spring. A control assembly according to the inventionhaving a contact-free pulse generator may also be utilized for governinga solenoid motor having one or several, alternatingly operative drivingcoils and an armature which may possibly be driven by a spring in onedirection.

It is also within the scope of the invention to drive the loop-taker bymeans of an electric motor, preferably a DC motor. On the motor shaftthere is then secured a pole-Wheel having a plurality of magnetic poles.When rotating, the pole wheel generates electric pulses in an adjacent,associated winding. The number of pulses per revolution corresponds tothe number of poles of the pole wheel.

The pulses are made rectangular in pulse shaping circuitry and areapplied to an electronic switching unit by which they are applied in apredetermined sequence to an electromagnetic step motor. This motorcomprises a permanent-magnetic armature rotor having a plurality ofpoles and e.g. two stators which may each have a pair of pole pieces.The stator field is created by direct current flux in the stator polepieces. By alternating, successive reversal of the direction of themagnetic flux in the stators, the rotor is made to rotate stepwise. Eachpulse created through the poles and the pulse transmitter at therotation of the pole wheel rotates the rotor of the step motor through apredetermined angle. If the number of poles of the pole wheel equals thenumber of magnetic poles (e.g. 24 or more) of the rotor of the stepmotor, each revolution of the pole wheel corresponds to a total angularincrement of 360 of the rotor of the step motor. The shaft of the stepmotor drives the needle-bar mechanically in its reciprocating movementin a manner known per se as well as the thread take up device. Thissystem brings about a complete synchronisation of the movements of theneedle-bar and the loop-taker.

The pole wheel and the step motor may be stopped in correct mutualpositions with the aid of a brake operating upon the shaft of the polewheel, or by maintaining a field winding of the step motorinterconnected. When starting it is possible to make the pole wheelsupply a special recognition or sync-pulse for each revolution of theloop-taker and make the rotor of the step motor (which has then aspecific design) initially lag, before it is synchronized with the polewheel when a predetermined rotational speed has been attained.

While the invention has been described with reference to two preferredembodiments thereof, it will be understood by those skilled in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope of the invention.

What we claim is:

1. In a sewing machine of the type adapted to have a reciprocatingneedle, electric driving means comprising:

at least two cooperating working devices, comprising a loop-taker and asewing needle holder including a needle bar, said needle holder beingmounted for reciprocation longitudinally of the longitudinal axis of theneedle;

a pulse motor drivingly connected to one of said looptakerand saidneedle holder and in combination therewith comprising first workingmeans;

an electric motor drivingly connected to the other of said loop-takerand said needle holder and in combination therewith comprising secondworking means;

a pulse generator for generating exciting pulses;

means driving said pulse geenrator in synchronism with said secondworking means;

a current source;

an electronic control assembly interconnected between said pulsegenerator and said pulse motor for receiving current from said currentsource and exciting pulses from said pulse generator and to put outcurrent pulses; and

means transmitting said current pulses to said pulse motor as drivinginput thereof whereby said one working means is driven in timedrelationship with said second working means.

2. The driving means of claim 1 wherein said first working meanscomprises a substantially vertically reciprocable needle holder havingmeans providing an upper limit position and said second working meanscomprises a loop-taker; wherein said pulse motor comprises an electromagnet motor having a reciprocable output motion; said electric motorbeing connected to said current source; motor speed control meansinterconnected between said electric motor and said current source formanual adjustment of the speed of said electric motor down to zero;means for stationing said needle holder in said upper limit positionwhen said loop-taker is not operating and consequently no exiting pulsesare received by said electronic control assembly from said pulsegenerator.

3. The driving means of claim 2 further having third working meanscomprising a work feeder to feed work in a step-wise manner; controlmeans responsive to the movement of the needle holder toward theloop-taker for inhibiting stepping of said work feeder when downwardmovement of said needle holder is arrested short of stitchformingcooperation with said loop-taker by abnormally great resistance from thework.

4. The driving means of claim 3 wherein the control means comprises atransducer secured to the needle bar and a contact-free impulsetransmitter sensitive to the proximity of said transducer; electricalmeans for stepping said work feeder; and means operatively connectingsaid electrical stepping means and said contact-free impulse transmitterfor initiating stepping by said electrical stepping means only when theneedle holder is positioned for said stitch-forming cooperation.

5. The driving means of claim 1 wherein said pulse motor is anelectrodynamic motor comprising a magnet body having means defining anannular air gap therein and a current coil operatively associated withsaid magnet body so as to be axially movable in said annular air gap;said needle bar being secured to said current coil.

6. The driving means of claim 5 wherein said control assembly providescurrent pulses of alternating polarity and having a frequency whichvaries directly with the velocity of said transducer.

7. The driving means of claim 6 wherein said control assembly comprisesa bi-stable multivibrator circuit and circuit means operativelyconnected thereto for successively reversing the current to the coil.

8. The driving means of claim 1, wherein the electronic control assemblyfor the pulse motor is transistorized and is connected to a directcurrent source of low voltage.

9. The driving means of claim 1, wherein said pulse motor drives saidneedle bar; and further comprising a second and a third pulse motorrespectively operatively connected to a work feeder and a thread take-updevice respectively via second and third pulse transmitters and secondand third electronic control assemblies.

10. The driving means of claim 9 including a transducer secured to theneedle bar; the second and third pulse transmitter sensing the proximityof said transducer.

11. In a sewing machine: rotatable working means including a loop-taker;reciprocable Working means including at least one of a sewing needleholder and workfeeder; a pulse motor for driving said reciprocableworking means, said pulse motor comprising a first stationary member anda second member movable with respect to said stationary member, one ofsaid members being a current coil and the other member being a magnetbody associated with said current coil; an ordinary electric motor fordriving at least said rotatable working means; a pulse generator forgenerating exciting pulses, said pulse generator being driven by saidordinary electric motor in synchronism with said rotatable workingmeans; a current source; an electronic control assembly interconnectedbetween said pulse generator and the current coil of said pulse motorand fed with current from said current source and with said excitingpulses for transforming them to current pulses to be applied to thecurrent coil of said pulse motor for driving said reciprocable workingmeans, and means mechanically connecting said reciprocable working meansto said movable member of said pulse motor, in timed relationship withsaid rotatable working means.

12. Driving means for a sewing machine according to claim 10characterized in that the movable member of the pulse motor and itsassociated reciprocable working means are reciprocated solely by currentpulses of alternating polarity applied to said current coil from saidelectronic control assembly, said pulses having a frequency which variesin response to the velocity of said pulse generator.

13. Driving means for a sewing machine according to claim 12,characterized in that said electronic control assembly comprises abi-stable multivibrator circuit and circuitry connected thereto forsuccessively reversing the current to said current coil.

14. Driving means for a sewing machine according to claim 11,characterized in that the movable member of said pulse motor and itsassociated reciprocable working means are advanced in at least onedirection by said current pulses applied to said current coil from saidelectronic control assembly, said pulses having a frequency which variesin response to the velocity of said pulse generator.

15. Driving means for a sewing machine according to claim 11,characterized in that the movable member of the pulse motor and itsassociated reciprocable working means are advanced by current pulses ofthe same polarity applied to said current coil from said electroniccontrol assembly, said pulses having a frequency which varies inresponse to the velocity of said pulse generator; in that rectifyingmeans is provided for filtering of the current pulses of oppositepolarity; and in that spring means are provided for retracting saidreciprocable working means.

16. In a sewing machine: a plurality of cooperating working meansincluding a loop-taker and a sewing needle holder reciprocable in thelongitudinal direction of the needle; a pulse motor for driving at leastone of said working means; an electric motor for driving at least asecond one of said working means; a pulse transmitter, a transducerdriven by said electric motor in synchronism with said second workingmeans and associated with said pulse transmitter for generating pulsestherein; a bistable multivibrator circuit electrically connected withsaid pulse transmitter and triggered by the pulses thereof; switchingcircuitry electrically connected to said multivibrator circuitry forreversing the polarity of every second pulse received therefrom; adirect current source for feeding said multivibrator circuit and saidswitching circuitry, which form together an electronic,break-contact-free control assembly electrically connected with said oneworking means and applying current pulses of alternating polaritythereto for driving it in timed relation with the other of said workingmeans.

17. Driving means for a sewing machine according to claim 16,characterized in that the working means driven by said pulse motorscomprises a needle-bar, a work feeder and a thread take-up device; andin that each of said pulse-motor-driven working means has an individualpulse motor, an individual transmitter and an individual electroniccontrol assembly.

18. Driving means for a sewing machine according to claim 17,characterized in that said work feeder and said thread take-up devicehave a common transducer driven by the pulse motor of the thirdpulse-motor-driven working means.

19. In a sewing machine: a plurality of cooperating working meansincluding a loop-taker and a sewing needle holder reciprocable in thelongitudinal direction of the needle; a pulse motor for driving at leastone of said working means; an electric motor for driving at least asecond one of said working means; a pulse transmitter; a transducerdriven by said electric motor in synchronism with said second workingmeans and associated with said pulse transmitter for generating pulsestherein; a current source; an electronic control assembly interconnectedbetween said pulse generator and said pulse motor and fed with currentfrom said current source and with said exciting pulses for transformingthem to current pulses to be applied to said pulse motor for drivingsaid one working means in step with said second working means.

20. In a sewing machine: a plurality of cooperating working meansincluding a loop-taker and a sewing needle holder reciprocable in thelongitudinal direction of the needle; a pulse motor for driving at leastone of said working means; an electric motor for driving at least asecond one of said working means; a pulse generator for generatingexciting pulses, said pulse generator being driven by said electricmotor in synchronism with said second working means; a bistablemultivibrator circuit electrically connected with said pulse generatorand triggered by the pulses thereof; switching circuitry electricallyconnected to said multivibrator circuitry for reversing the polarity ofevery second pulse received therefrom; a direct current source forfeeding said multivibrator circuit and said switching circuitry, whichform together an electronic, break-contact-free control assemblyelectrically connected with said one working means and applying currentpulses of alternating polarity thereto for driving it in step with saidsecond working means.

References Cited UNITED STATES PATENTS 1,196,160 8/1916 Schoolfield etal. 112-220 2,262,616 11/1941 List 112-220 3,149,274 9/1964 Hetzel318-132 3,184,623 5/1965 Marti et al 318-132 FOREIGN REFERENCES 777,65412/1934 France.

PATRICK D. LAWSON, Primary Examiner.

H. HAMPTON HUNTER, Assistant Examiner.

US. Cl. X.R.

1. IN A SEWING MACHINE OF THE TYPE ADAPTED TO HAVE A RECIPROCATING NEEDLE, ELECTRIC DRIVING MEANS COMPRISING: AT LEAST TWO COOPERATING WORKING DEVICES, COMPRISING A LOOP-TAKER AND A SEWING NEEDLE HOLDER INCLUDING A NEEDLE BAR, SAID NEEDLE HOLDER BEING MOUNTED FOR RECIPROCATION LONGITUDINALLY OF THE LONGITUDINAL AXIS OF THE NEEDLE; A PULSE MOTOR DRIVINGLY CONNECTED TO ONE OF SAID LOOPTAKER AND SAID NEEDLE HOLDER AND IN COMBINATION THEREWITH COMPRISING FIRST WORKING MEANS; AN ELECTRIC MOTOR DRIVINGLY CONNECTED TO THE OTHER OF SAID LOOP-TAKER AND SAID NEEDLE HOLDER AND IN COMBINATION THEREWITH COMPRISING SECOND WORKING MEANS; A PULSE GENERATOR FOR GENERATING EXCITING PULSES; MEANS DRIVING SAID PULSE GENERATOR IN SYNCHRONISM WITH SAID SECOND WORKING MEANS; A CURRENT SOURCE; 